it is only put coordinating conjuction or subcoordinating or adverbs ;) thanks so much
8. Math is a pain. Grammar is worse. (compound sentence: coordinating conjunction)
Answer: Math is a pain; moreover, grammar is worse.
9. I arrived. The big dog barked. (complex sentence)
Answer: When I arrived, the big dog barked.
10. John bought some new shoes. He wore them to a party. (compound sentence: coordinating conjunction)
Answer: John bought some new shoes, for he wore them to a party.
11. The apples weren't selling very well. He decided to have a sale. (compound sentence: conjunctive adverb)